System of firefighting and blow-out protection for a drilling operation

ABSTRACT

A system of fire fighting and blow-out protection for a drilling operation comprising valves and flow conduits interconnecting a low pressure and a high pressure source of inert gas to the interior of a blow-out preventer assembly. A pneumatically actuated valve connected to the blow-out preventer outflow conduit is moved to the closed position upon a predetermined pressure being effected by the flow of inert gas therewithin. Gaseous hydrocarbons leaking from the blow-out preventer are rendered noncombustible by admixing an inert diluent therewith by moving a flow control valve to a first position. Should the situation deteriorate into a more dangerous condition, the valve can be further opened whereupon a high pressure source of inert gas is flow conducted into the blow-out preventer while at the same time the outflow valve from the blow-out preventer is moved to the closed position, thereby setting the rubber of the blowout preventer assembly and increasing the effective hydrostatic head of the borehole, as well as lowering the inflammable limits of the escaping gaseous hydrocarbons.

[ Apr. 16, 1974 1 SYSTEM OF FIREFIGl-ITING AND BLOW-OUT PROTECTION FOR ADRILLING OPERATION Dolph S. Miller, 502 N. McKinney, Odessa, Tex. 79763221 Filed: July 12, 1972 21 Appl. No.: 270,956

[76] Inventor:

[58] Field of Search 169/1 A, 2 R, 11 166/O.5, 166/53, 64, 9O

[56] References Cited UNITED STATES PATENTS 1,552,342 9/1925 Porter166/90 1,640,839 8/1927 Kliewer..... 169/2 R 1,787,927 1/1931Bu1lard.... 169/2 R 1,879,160 9/1932 Fowzer 169/2R 2,699,216, 1/1955Al1en.... 169/1 A 3,070,172 12/1962 Carter 169/1 A 3,457,993 7/1969Parker et al. J 166/64 3,620,299 11/1971 Wiseman 169/2 R 3,621,91211/1971 Wooddy et a1. 166/O.5 3,638,721 2/1972 Harrison .L. 166/0.53,651,823 3/1972 Milsted 166/53 Primary Examinr-Robert S. Ward, Jr.Attorney, Agent, or Firm-Marcus L. Bates 57 ABSTRACT A system of firefighting and blow-out protection for a drilling operation comprisingvalves and flow conduits interconnecting a low pressure and a highpressure source of inert gas to the interior of a blow-out preventerassembly. A pneumatically actuated valve connected to the blow-outpreventer outflow conduit is moved to the closed position upon apredetermined pressure being effected by the flow of inert gastherewithin.

Gaseous hydrocarbons leaking from the blow-out preventer are renderednoncombustible by admixing an inert diluent therewith by moving a flowcontrol valve to a first position. Should the situation deteriorate intoa more dangerous condition, the valve can be further opened whereupon ahigh pressure source of inert gas is flow conducted into the blow-outpreventer while at the same time the outflow valve from the blow-outpreventer is moved to the closed position, thereby setting the rubber ofthe blow-out preventer assembly and increasing the effective hydrostatichead of the borehole, as well as lowering the inflammable limits of theescaping gaseous hydrocarbons.

' 6 Claims, 3 Drawing Figures SYSTEM OF FIREFIGHTING AND BLOW-OUTPROTECTION FOR A DRILLING OPERATION BACKGROUND OF'THE DISCLOSUREThroughout this disclosure, the term BOP" refers to and'will relate to ablow-out prevention apparatus of the type described herein.

In drilling operations it is customary to provide one or more blow-outprevention apparatus which are connected to the well casing with thedrill string extending therethrough. Should a gas pocket or a highpressure gaseous formation be encountered while making hole, the BOP,when actuated, will prevent losing control of the well from a wellblow-out.

Some BOPs are manually actuated by mechanically forcing an annular bodyof resilient material to be tightly compressed between the interior bodyof the BOP and exterior surface of the drill string, thereby effecting aseal means for preventing fluid from flowing up the casing annulus.Other BOPs include pneumatically or motor driven resilient bodies whichare forced towards one another and about the drill string so as to forma closure member at the upper extremity of the casing annulus.

During the drilling operation, from time to time a high pressure gaspocket may be encountered, whereupon gaseous hydrocarbons are returnedto the surface of the earth along with the drilling fluid. The flow ofgaseous hydrocarbons in proximity of the drilling operation is dangerousbecause the mixture, when admixed with atmospheric air, becomesexplosive in nature and for this reason it is desirable to be able toadmix an inert gas withthe escaping hydrocarbons so as to adjust thepercentage composition of the resultant mixture to a value which isnoncombustible.

At other times the pressure in the gas pocket may be of sufficientmagnitude to cause potential loss of control over the well, that is, thewell will make sufficient gas so as to percolate the drilling fluid fromthe borehole, sometime carrying therewith the entire tubing string andportions of the derrick. Sometimes death and destruction accompanies aserious blow-out, and 99 percent of destructive rig fires are'caused bythis phenomenon.

ln BOPs of the prior art, 30 to 60 seconds are required for shutting inthe well. When a high pressure gas formation is encountered and ablow-out occurs, ignition of the escaping gaseous hydrocarbons can meltthe rig to the ground in as 'iittle as three minutes. When a blow-outoccurs and the hydrocarbons completely engulf the rig area, it isusually understood that a condition has been encountered where itseveryman for himself.

However, a blow-out seldom occurs instantaneously. There is I oftensufficient warning to enable an alert driller to shut-in the well byseveral wellknown expedients. In the initial stages of the blow-out itwould be desirable to be able to sufficiently dilute the flow of gaseoushydrocarbons to preclude combustion thereof. Moreover, it would bedesirable for the inflow of the inert gas to be of sufficient magnitudeto effectively increase the hydrostatic head of the well, therebygreatly aiding the driller in rapidly attaining a shut-in condition.

It is furthermore desirable to be able to provide deep wells andoff-shore drilling platforms with reliable, safe,

low cost equipment which would shut-in a well in less time than isrequired for workmen to abandon the rig.

Summary of the Invention The present invention encompasses both methodand apparatus which provides an inert gas fire fighting and blow-outprotection system for drilling apparatus.

The invention is carried out in conjunction with a drilling operationwherein a cased borehole has a BOP affixed thereto with drill tubingaxially extending through the BOP and into the casing, with an annularaxial flow passageway extending from the casing annulus longitudinallythrough the BOP.

A rotating seal means at the upper marginal end of the BOP annulusprevents fluid flow from the upper extremity thereof while a drillingfluid outflow passageway enables drilling fluid to flow from theborehole annulus, into the BOP, through the outflow passageway, and tothe mud pit.

An inert gas inlet passageway is flow connected to the annulus of theBOP and has associated therewith means by which inert gas can be admixedwith any gases contained within the BOP annulus whenever desired.

The system includes means responsive to a high flow rate of inert gasinto the BOP which causes the outflow valve to automatically assume theclosed position while subsequently or simultaneously the high pressuresource of inert gas which is conducted to the annulus of the BOPeffectively increases the hydrostatic head of the well.

A primary object of the present invention is to provide an inert gasfire fighting and blow-out protection system for drilling operations. 4

Another object of the invention is to provide a method of increasing theeffective hydrostatic head of a borehole.

A further object of this invention is to provide a method of shutting-ina well during a drilling operation.

A still further object of this invention is to disclose and provide amethod and apparatusfor reducing the combustibility of hydrocarbon gasesflowing from the borehole of a drilling operation.

Another and still further object of this invention is to provide aninert gas flow system used in conjunction with a drilling operation toenable a combustible mixture of hydrocarbons to be renderedincombustible.

These and various other objects and advantages of the invention willbecome readily apparent to those skilled in the art upon reading thefollowing detailed description and claims and by referring to theaccompanying drawing.

The above objects are attained in accordance with the present inventionbythe provision of a method of fire fighting and blow-out protection fora drilling operation for use with apparatus fabricated in a mannersubstantially as described in the above abstract and summary.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematical presentation inthe form of a flow sheet which sets forth the method of the presentinvention;

FIG. 3 is a reduced top plan view of the apparatus disclosed in FIG. 2.

Detailed Description of the Invention FIG. 1 illustrates a borehole lsunk into the ground and having drill string 13 therein to which a drillbit may be attached for making hole.

A drilling rig (not shown) has the usual deck or'floor 14 for rotatablysupporting a turntable l thereon. Disposed below the turntable there isschematically represented two series connected BOPs, l6 and 17, whichmay be arranged in the disclosed manner, or if desired, the relationshipthereof can be reversed. The BOP 16 is not essential for practicing thepresent invention.

The BOP l7 of'the present invention has an outflow valve 18 throughwhich mud or drilling fluid canflow from the borehole to the mudpit (notshown).

Inert gas inlet 19 is connected to inflow conduit 20. Control flow valve21 is preferably remote controlled from the rig floor so that 'it formsan inflow control device. The valve is interposed between a source ofinert gas 22 and inflow connection 19. Check valve 21 permits flow inthe indicated direction but precludes flow from occurring towards remotecontrol flow valve 21.

Ahigh pressure source of inert gas 23, preferably at least 2,000 cu. ft.of gas atl ,500 to 2,500 psi, is conveniently disposed in closeproximity of the low pressure source of gas, preferably at least 500 cu.ft. gas at below 250 psi. Valve 24 .is normally open and seriesconnectedrelative to check valve 25 so as to provide a low pressure source ofinert gas at junction 26 when the system is in the stand-byconfiguration.

Motor control valve 27 is normally closed and series connected relativeto normally open valve 28 so that when valve 27 is moved to the openposition, the high pressure source of inert gas flows. from storage 23to junction 26.

Junction 29 interconnects flow conduit 30 with junction 26 so as toprovidea source of pressure at the illustr ated motor valves 27, 31.Motor valve 31 normally is in the open position so that drilling fluidfrom the BOP is free to flow to the mud pit along conduit 32.

The BOP illustrated in FIGS. 2 and 3 includes a massive body member 33having a circumferentially extending flange 34 which can be bolted ontothe terminal end of the borehole casing. The upper marginal end portion35 of the body is proviced with a rotating seal member, which includes abarrel 36 rotatably received within member 35. Journals 37, 38preferably are tapered roller bearings set at an angle relative to oneanother in the usual manner so as to secure the barrel against axialmovement.

Seal member 39 is removably affixed to the barrel and precludes fluidflow between the barrel and member 35. The seal can take on any numberof different forms so long as this intended purpose is attained. Adrilling rubber in the form'of a resilient deformable member 40 has alower terminal end portion 41 which terminates within the BOP annulusand slidably and telescopingly receives the drill string therethroughwith the inside peripheral wall portion 42 sealingly bearing against theouter peripheral wall surface of the string. The resilient seal memberincludes a circumferentially 4 extending seal portion 44 which isremovably affixed to the barrel.

The outflow conduit includes passageway 45 which flow communicates withthe annular BOP passageway 46, which in turn flow communicates with thecasing annulus 112. A plurality of inert gas inflow passageways, one ofwhich is illustrated by numeral 47 flow communicates with annulus 46 andan inflow conduit 19 so that increased pressure can be effected at theseal chamber annulus 43.

Inert gas generator 122 provides additional embodiments of theinvention, and can be in the form of a combustion chamber whereingaseous hydrocarbons are completely combusted into CO and N with thewater of combustion being removed by a conventional knock-out drum.Alternatively, the generator 122 can be the exhaust of an internalcombustion engine with arrangements being made for precluding ingestionof atmospheric air into the system.

Pump 123 compresses the effluent from 122 so that makeup inert is alwaysavailable at 23. Constant pressure regulator valve 124 provides acontinuous source of low pressure inert gas at 22.

In operation, while making hole with the drilling apparatus, outflowvalve 31 is normally open, inflow valve 21 is normally closed, valve 24is normally open, valve 27 is normally closed, and valve 28 is normallyopen. Accordingly, valve 21 can be moved to the open position whereuponflow occurs from the low pressure source, through the normally openvalve 24, through one-way check valve 25 to junction 26, through thepartiallyopen valve 21, through the one-way check valve 21', and intothe annulus 43, 46 whereupon the inert gas admixes with and flows alongwith any gaseous products from the BOP.

The pneumatically actuated valves 27, 31 are set to respond at apressure in excess of any arbitrarily selected meaningful pressuredifferential normally effected between the annulus 43 and ambient. Forexample, valve 31 may be set to close at a pressure of 30 psi above thenormal pressureeffected within passageway 45, while valve 27 is set toopen at a pressure 60 psi above the pressure normally encountered inpassageway 47. f

- As valve 21 is more'fully opened to a second position, the pressurewithin passageway 45 increases, thereby reflecting an increased pressureat 29, whereupon the motor of the valve, such as the diaphragm, causesthe valve 31 to assume the closed position. Since the mud pumps arestill running, pressure at junction 29 is further increased, therebycausing motor valve 27 to assume the opened position, whereupon the highpressure inert gas 23 flo'ws through normally open valve 28, throughvalve 27, to junction 26 and on to the annulus 46 and 43, therebyeffecting a tremendous pressure within the BOP annulus 43. It will beappreciated that a pressure source of gas at l,000 psi, for example, isequivalent to about 2,000 feet increased hydrostatic head within thewell bore.

This action of the high pressure inert gas causes the inner peripheralwall surface of the rubber to be forced against the outer. peripheralwall surface of the drill string with a tremendous force which isproportional to the pressure within the BOP annulus.

Seal 39 wears rapidly and usually is the first interface to causeleakage of hydrocarbons to occur from the borehole into the atmosphere.Progressive wear about this member enables gaseous hydrocarbons to flowfrom annulus 46, about the seal, and between the interface formedbetween the barrel and the housing. When leakage is noted, or shouldignition of the escaping gases occur, the danger is obviated by admixinginert gas therewith so that the drilling operation can proceeduninterrupted until another trip into the hole becomes necessary,whereupon the seal can be easily replacedwith no down-time.

Accordingly, should the well commence making gas, the valve 21 can bepartially opened so as to render leakage from the BOP incombustible,that is, the percentage composition of hydrocarbons in the resultantmixture is incombustible in atmospheric air. Should the well commenceunequal flow distribution of drilling fluid, or should any otherindication of potential loss of control evidence itself, the valve 21can be further opened, thereby rapidly causing the well to assume the"shut-in configuration.

The response time for actuation of the motor valves 27, 31 can beregulated to any desired time interval, but it is preferred to havevalve 21 arranged to enable shut-in of thewell within two to fiveseconds. Hence, the roughnecks are secure in the knowledge that the wellcan be shut-in more rapidly than they are capable of abandoning the rig.

Hence, the present invention is useful in preventing combustiblemixtures of hydrocarbons from accumulating in proximity of the drillingrig as well as enabling the well to assume the shut-in" configuration.

I claim:

1. In a drilling operation having a blowout preventer affixed to acasing; with the casing extending downhole in a borehole; drill tubingextending through the blowout preventer and into the casing; an annularflow passageway extending from the casing annulus and through theblowout preventer; a flow passageway extending from the annular flowpassageway to an outflow pipe; and a seal member for preventing fluidfrom flowing from the upper extremity of the annular flow passageway;the method of extinguishing fires comprismg:

flow connecting a source of inert gas to said'annular flow passageway;

interposing an inflow control device between the source of inert gas andsaid annular flow passagey flowing inert gas into the annular flowpassageway at a rate which renders any resulting gaseous mixture 5formed within the outflow pipe incombustible in atmospheric air;interposing an outflow control device in said outflow line so that theinert gas effects an increased pressure within the annular flowpassageway;

actuating the outflow valve to the closed position in response to flowoccurring through said inflow control device; and

increasing the inert gas pressure within the annular flow passageway soas to increase the effective hydrostatic head of the well.

2. The method of claim 1 and further including the steps of:

actuating the inflow control device to the open position when it isdesired to attain a first flow of a noncombustible mixture of gases intothe blowout preventer; pneumatically actuating the outflow valve .to theclosed position when it is desired to attain a second flow ofanon-combustible mixture of gases into the blowout preventer; and vpneumatically connecting a high pressure source of gas to the blowoutpreventer in response to the presence of said second flow of gases.

3.- The method of claim 1 wherein said inert gas is selected from thegroup consisting of N CO and flue gas.

4. The method of claim 1 wherein said inert gas is flue gases derivedfrom the combustion of atmospheric air and hydrocarbons.

5. The method of claim 4 wherein said flue gases are obtained from theexhaust system of an internal combustion engine and further includingthe step of:

compressing said flue gases so as to provide said source of highpressure inert gas.

6. The method of claim 5 and further including the step ofinterconnecting the high pressure source of inert gas with the lowpressure source of inert gas by means of a pressure regulator valve. 45

1. In a drilling operation having a blowout preventer affixed to acasing; with the casing extending downhole in a borehole; drill tubingextending through the blowout preventer and into the casing; an annularflow passageway extending from the casing annulus and through theblowout preventer; a flow passageway extending from the annular flowpassageway to an outflow pipe; and a seal member for preventing fluidfrom flowing from the upper extremity of the annular flow passageway;the method of extinguishing fires comprising: flow connecting a sourceof inert gas to said annular flow passageway; interposing an inflowcontrol device between the source of inert gas and said annular flowpassageway; flowing inert gas into the annular flow passageway at a ratewhich renders any resulting gaseous mixture formed within the outflowpipe incombustible in atmospheric air; interposing an outflow controldevice in said outflow line so that the inert gas effects an increasedpressure within the annular flow passageway; actuating the outflow valveto the closed position in response to flow occurring through said inflowcontrol device; and increasing the inert gas pressure within the annularflow passageway so as to increase the effective hydrostatic head of thewell.
 2. The method of claim 1 and further including the steps of:actuating the inflow control device to the open position when it isdesired to attain a first flow of a non-combustible mixture of gasesinto the blowout preventer; pneumatically actuating the outflow valve tothe closed position when it is desired to attain a second flow of anon-combustible mixture of gases into the blowout preventer; andpneumatically connecting a high pressure source of gas to the blowoutpreventer in response to the presence of said second flow of gases. 3.The method of claim 1 wherein said inert gas is selected from the groupconsisting of N2, CO2, and flue gas.
 4. The method of claim 1 whereinsaid inert gas is flue gases derived from the combustion of atmosphericair and hydrocarbons.
 5. The method of claim 4 wherein said flue gasesare obtained from the exhaust system of an internal combustion engineand further including the step of: compressing said flue gases so as toprovide said source of high pressure inert gas.
 6. The method of claim 5and further including the step of interconnecting the high pressuresource of inert gas with the low pressure source of inert gas by meansof a pressure regulator valve.